Many field-emission device structures, including diodes, triodes, and tetrodes, have been developed for use in electronic circuits. Some of the field-emission devices have been adapted specifically for use in displays. In such displays, each pixel cell uses one or more field-emission devices. Field-emission displays are considered an attractive alternative and replacement for flat-panel liquid crystal displays, because of their lower manufacturing cost and lower complexity, lower power consumption, higher brightness, and improved range of viewing angles. There is a continuing need for improved microelectronic device structures and fabrication processes, especially for flat panel displays.